The Ship Structure Committee (SSC) identified a lack of information required for structural integrity and damage tolerance analyses of aluminum marine structures. The development of such data is vital in light of the increased use of aluminum alloys in marine construction. Under SSC project SR-1447, Fracture Technology Associates was contracted to characterize, through experimental fracture mechanics, the fatigue crack growth (FCG) resistance and fracture toughness of three aluminum alloys (5083, 5086, 5383) used in marine structural applications. Fatigue crack growth testing was performed following ASTM Standard E 647-00 in laboratory air at room temperature and in simulated ocean water per ASTM Standard D 1141. Non-linear fracture toughness testing was performed in accordance with ASTM Standard E 1820-01 in laboratory air at room temperature. For the three different grades of material, the difference in fatigue crack growth rate in laboratory air was negligible. In simulated seawater environment, AA5086 showed a slightly superior performance. In addition, all samples showed the same ranking of toughness with the 5086 showing the highest toughness, followed by 5083 and then 5383.